A carrying robot is used in a carrying chamber continuously provided to a processing chamber for carrying a processed object of a semiconductor wafer, a liquid crystal substrate or the like to respective processing chambers. A processed object of a semiconductor wafer, a liquid crystal substrate or the like abhors particles and needs to be processed finely. Therefore, a carrying robot is used under a vacuum environment. Further, maintenance of a carrying robot is carried out such that a particle is not generated in a vacuum environment.
According to a drive apparatus used in a carrying robot of a background art, a partition wall of a carrying chamber is provided with a bearing housing, a rotation input shaft is provided at the bearing housing rotatably through two bearings, the rotation input shaft is sealed in airtight by a magnetic fluid seal provided between the two bearings, thereby, a seal unit is constituted. Further, a lower end of the rotation input shaft is connected with a drive motor through a speed reducer (refer to, for example, Patent Reference 1).
Further, as other drive apparatus of a carrying robot, a vacuum drive apparatus having a function of hermetically sealing an interval between a motor stator and a motor rotor by a metal partition wall is widely and generally used (refer to, for example, Patent Reference 2).
However, according to the drive apparatus used under the vacuum environment of the background art as in Patent Reference 1, it is necessary to arrange a plurality of pieces of magnetic fluid seals in series in order to ensure an airtight function of a vacuum state, and therefore, a structure thereof is complicated, large-sized and expensive. Further, the magnetic fluid seal uses a special fluid, and therefore, maintenance by an end user cannot be carried out, a mist of a magnetic fluid is always discharged in vacuum, and therefore, a problem of contaminating a carrying chamber is posed.
Further, according to the vacuum drive apparatus having the hermitically sealing function by the metal partition wall between the motor stator and the motor rotor as in Patent Reference 2, although the airtight function is excellent, a bearing for rotatably supporting an output pivoting member operated with an external load needs to be arranged in vacuum. Therefore, an expensive bearing for vacuum is needed, an area thereof exposed to vacuum is increased, running cost for vacuuming is increased and the drive apparatus becomes expensive. Furthermore, when it is necessary to transmit a torque having a large output, a problem that a direct drive motor per se is large-sized more than the speed reducer is posed.
In order to resolve the problem of the background art disclosed in Patent Reference 1 or 2, Patent Reference 3 discloses to provide a gear apparatus for vacuum capable of being used as a drive portion of a fabrication apparatus for fabricating a processed object of a semiconductor wafer, a liquid crystal substrate or the like under a vacuum environment, which is small-sized and inexpensive and excellent in a maintenance performance.
According to the gear apparatus for vacuum of Patent Reference 3, the apparatus is characterized in that a contact type vacuum seal is provided between a stationary member and an output member of a gear apparatus for vacuum used under a vacuum environment. By constructing such a constitution, the drive apparatus used under the vacuum environment can be made to be small-sized. Further, the vacuum seal can be arranged by following a core of the stationary member and the output member of the gear apparatus for vacuum, and therefore, an operation of centering a seal unit of the background art and the speed reducer is dispensed with and a maintenance performance is promoted.    Patent Reference 1: JP-A-6-285780    Patent Reference 2: Japanese Patent Registration No. 2761438    Patent Reference 3: JP-A-2004-84920